Since 1990s, code division multiple access (CDMA) systems have gained wide attention, and many relevant studies have been carried out. CDMA2000 is one of mainstream third generation (3G) technologies, which has already become commercially available all over the world. CDMA2000-1× is the first phase of the development of CDMA2000 systems, is corresponding to protocol versions “CDMA2000 Release 0”, “CDMA2000 Release A” and “CDMA2000 Release B”, and is backward compatible with the existing Interim Standard (IS)-95. A high data rate (HDR) technology is accepted by the Telecommunications Industry Association (TIA)/Electronic Industries Association (EIA) as an IS-856 standard (Release 0). The HDR technology is also referred to as high rate packet data (HRPD) or 1× EV-DO, in which 1× means that the HRPD technology uses the same radio frequency bandwidth and chip rate as CDMA2000 1× systems, and has good backward compatibility; EV (evolution) means that the HRPD technology is an evolved version of CDMA2000 1×; DO (data optimization) means that the HRPD technology specifically optimized for packet data services. 1× EV-DO is accepted by the International Telecommunication Union-Recommendation (ITU-R) as one of 3G technology standards.
In addition, a long term evolution (LTE) technology is regarded as a mainstream technology of fourth generation (4G) mobile communication systems. The LTE system adopts orthogonal frequency division multiple access (OFDMA) and multiple input multiple output (MIMO) technologies, and therefore can greatly improve spectrum utilization and capacity of a communication system. Moreover, the LTE technology can better support large data download services such as the Voice over Internet Protocol (VoIP) or video calling. The LTE technology is regarded as a mainstream next-generation technology, and therefore, some leading CDMA/HRPD operators decide to gradually upgrade the existing HRPD networks to LTE networks. During a network upgrade process, some users need to use an HRPD-LTE dual-mode terminal to perform full network roaming because two types of networks HRPD and LTE coexist, with the LTE network having a partial coverage and the HRPD network having a complete coverage.
An optimized LTE-HRPD handover means that when a dual-mode terminal enters an edge zone covered by an LTE network, an HRPD module in the dual-mode terminal performs network registration in advance through a tunnel between the LTE network and the HRPD network, so that when the dual-mode terminal leaves the LTE coverage area and an LTE-HRPD handover is performed, because no operation such as registration is required, the handover speed can be greatly increased, and the call drop rate can be greatly reduced, thereby improving the conversation quality. During the optimized LTE-HRPD handover, after the HRPD module completes pre-registration, that is, completes initialization of an HRPD protocol, an LTE module in the dual-mode terminal needs to periodically enable the HRPD module to perform pilot measurement on the HRPD network and report a measurement result to the LTE network, so that the LTE network makes a handover decision.